Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However...Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.展开更多
We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are parti...We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are particularly investigated in various cases for distinguishing efficiently the acoustic localisation from the effects of acoustic absorption caused by the viscosity of medium. The numerical results reveal the phenomenon of ＇phase transition＇ characterized by an unusual collective oscillation of bubbles, which is an effective criterion to unambiguously identify the acoustic localisation in the presence of viscosity. Within the localisation region, the phenomenon of phase transition persists, and a remarkable decrease in the fluctuation of the oscillation phases of bubbles is observed. The localisation phenomenon will be impaired by the enhancement of the viscosity factors, and the extent to which the acoustic wave is localised may be determined by appropriately analyzing the values of the oscillation phases or the amount of reduction of the phase fluctuation. The results are particularly significant for the practical experiments in an attempt to observe the acoustic localisation in such a medium, which is in general subjected to the interference of the great ambiguity resulting from the effect of acoustic absorption.展开更多
The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnos...The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnosis in analog circuits is presented in this paper.The proposed method extracts the original signals from the output terminals of the circuits under test（CUT） by a data acquisition board.Firstly,the phase deviation value between fault-free and faulty conditions is obtained by fitting the sampling sequence with a sine curve.Secondly,the sampling sequence is organized into a square matrix and the spectral radius of this matrix is obtained.Thirdly,the smallest error of the spectral radius and the corresponding component value are obtained through comparing the spectral radius and phase deviation value with the trend curves of them,respectively,which are calculated from the simulation data.Finally,the fault location is completed by using the smallest error,and the corresponding component value is the parameter identification result.Both simulated and experimental results show the effectiveness of the proposed approach.It is particularly suitable for the fault location and parameter identification for analog integrated circuits.展开更多
随着分布式能源与随机负荷的大量接入,配电台区三相负荷不平衡与变压器轻重载运行问题日益突出,这将威胁台区安全可靠运行。然而,既有关于互联台区的研究鲜有兼顾三相不平衡与轻重载运行问题的综合治理。对此,该文提出一种基于四桥臂智...随着分布式能源与随机负荷的大量接入,配电台区三相负荷不平衡与变压器轻重载运行问题日益突出,这将威胁台区安全可靠运行。然而,既有关于互联台区的研究鲜有兼顾三相不平衡与轻重载运行问题的综合治理。对此,该文提出一种基于四桥臂智能软开关(four-leg soft open point,F-SOP)的柔性互联配电台区三相不平衡与轻重载综合调控策略。首先,分析了F-SOP和变压器的综合损耗特性,结果表明不平衡度和负载率均会影响设备运行效率;其次,建立三相不平衡与轻重载综合调控策略模型,设立变压器输出功率不平衡度与负载率的指标约束,以系统综合损耗最小为优化目标求解F-SOP最优调控指令。接着,针对F-SOP拓扑架构及其功率调控的需求,提出一种改进对等控制方法,进一步提高F-SOP稳定性能与动态性能,确保综合调控策略的实现。最后,通过算例分析与仿真实验验证了所提综合调控策略的有效性和可行性。展开更多
基金financially supported by Open Fund of Material Corrosion and Protection Key Laboratory of Sichuan Province of China(No.2020CL09)Hunan Key Laboratory of Applied Environmental Photocatalysis(No.2214503)。
文摘Vanadium flow batteries(VFBs)are considered ideal for grid-sc ale,long-duration energy storage applications owing to their decoupled output power and storage capacity,high safety,efficiency,and long cycle life.However,the widespread adoption of VFB s is hindered by the use of expensive Nafion membranes.Herein,we report a soft template-induced method to develop a porous polyvinylidene fluoride(PVDF)membrane for VFB applications.By incorporating water-soluble and flexible polyethylene glycol(PEG 400)as a soft template,we induced the aggregation of hydrophilic sulfonated poly(ether ether ketone),resulting in phase separation from the hydrophobic PVDF polymer during membrane formation.This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution.The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm^(2),and the VFB exhibited a Coulombic efficiency of 95.2%and a voltage efficiency of 87.8%.These findings provide valuable insights for the development of highly stable membranes for VFB applications.
基金supported by the National Natural Science Foundation of China (Grant Nos.10804050 and 10874086)the Ministry of Education of China (Grant Nos.20060284035 and 705017)
文摘We study via numerical experiments the localisation property of an acoustic wave in a viscoelastic soft medium containing randomly-distributed air bubbles. The behaviours of the oscillation phases of bubbles are particularly investigated in various cases for distinguishing efficiently the acoustic localisation from the effects of acoustic absorption caused by the viscosity of medium. The numerical results reveal the phenomenon of ＇phase transition＇ characterized by an unusual collective oscillation of bubbles, which is an effective criterion to unambiguously identify the acoustic localisation in the presence of viscosity. Within the localisation region, the phenomenon of phase transition persists, and a remarkable decrease in the fluctuation of the oscillation phases of bubbles is observed. The localisation phenomenon will be impaired by the enhancement of the viscosity factors, and the extent to which the acoustic wave is localised may be determined by appropriately analyzing the values of the oscillation phases or the amount of reduction of the phase fluctuation. The results are particularly significant for the practical experiments in an attempt to observe the acoustic localisation in such a medium, which is in general subjected to the interference of the great ambiguity resulting from the effect of acoustic absorption.
基金supported by the National Natural Science Foundation of China under Grant No.61371049
文摘The soft fault induced by parameter variation is one of the most challenging problems in the domain of fault diagnosis for analog circuits.A new fault location and parameter prediction approach for soft-faults diagnosis in analog circuits is presented in this paper.The proposed method extracts the original signals from the output terminals of the circuits under test（CUT） by a data acquisition board.Firstly,the phase deviation value between fault-free and faulty conditions is obtained by fitting the sampling sequence with a sine curve.Secondly,the sampling sequence is organized into a square matrix and the spectral radius of this matrix is obtained.Thirdly,the smallest error of the spectral radius and the corresponding component value are obtained through comparing the spectral radius and phase deviation value with the trend curves of them,respectively,which are calculated from the simulation data.Finally,the fault location is completed by using the smallest error,and the corresponding component value is the parameter identification result.Both simulated and experimental results show the effectiveness of the proposed approach.It is particularly suitable for the fault location and parameter identification for analog integrated circuits.
文摘随着分布式能源与随机负荷的大量接入,配电台区三相负荷不平衡与变压器轻重载运行问题日益突出,这将威胁台区安全可靠运行。然而,既有关于互联台区的研究鲜有兼顾三相不平衡与轻重载运行问题的综合治理。对此,该文提出一种基于四桥臂智能软开关(four-leg soft open point,F-SOP)的柔性互联配电台区三相不平衡与轻重载综合调控策略。首先,分析了F-SOP和变压器的综合损耗特性,结果表明不平衡度和负载率均会影响设备运行效率;其次,建立三相不平衡与轻重载综合调控策略模型,设立变压器输出功率不平衡度与负载率的指标约束,以系统综合损耗最小为优化目标求解F-SOP最优调控指令。接着,针对F-SOP拓扑架构及其功率调控的需求,提出一种改进对等控制方法,进一步提高F-SOP稳定性能与动态性能,确保综合调控策略的实现。最后,通过算例分析与仿真实验验证了所提综合调控策略的有效性和可行性。
